JPH02265043A - Magneto-optical recording medium - Google Patents

Abstract

PURPOSE:To obtain the magneto-optical recording medium having the sufficiently large reproducing C/N at the time of signal reproduction and an excellent recording sensitivity and erasing characteristics by forming a dielectric layer of an aluminum nitride layer contg. samarium. CONSTITUTION:The dielectric layer 2 is laminated on a transparent substrate 1. The formation of the layer 2 is executed by forming the AlN dielectric layer contg. 1.8 atomic% Sm to 90nm thickness by an RF magnetron sputtering method using a sintered AlN target embedded with Sm pieces. A magnetic thin film 3 is thereafter laminated thereon to 70nm thickness by a DC magnetron sputtering method without breaking the vacuum. The same film as the film of the layer 2 is further formed thereon to 100nm thickness as a protective film 4. While >=45dB reproducing C/N is assured in the range of 1.5 to 3.5 atomic% ratio of the Sm contained in the AlN dielectric layer 2, the uniform characteristics of nearly 4.0 to 5.0mW laser power necessary for signal recording and erasing are attained.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention records information photothermomagnetically using laser light,
The present invention relates to a magneto-optical recording medium in which recorded magnetic information is read using the magneto-optic effect.

[Conventional technology]

In recent years, the practical application of rewritable magneto-optical memory has been viewed as promising. The magneto-optical recording medium used in this magneto-optical memory is made of a rare earth-containing transition metal amorphous material such as TbFeCo. It is formed on a substrate such as resin, and information is recorded by thermomagnetic writing using a laser beam on the magnetic thin film, and the recorded information is reproduced from the magnetic thin film by magneto-optical maximum - (1 (err) effect). This is done by detecting the rotation of the polarization plane (Kerr rotation) of reflected light.

[Problem to be solved by the invention]

However, the Kerr rotation angle θ of magnetic thin films currently used as perpendicularly magnetized thin films is 0.3° to 0.4°, and the degree of modulation of the reproducing light due to the recording bits is as small as about 1%. The problem is that the read CN ratio is not sufficient.

It is reported that the error rate of the medium becomes constant if the playback CN ratio is 40 dB or more, and in order to increase reliability, it is necessary to
It is said that a value of dB or more is desirable. Therefore,
There is a method of improving the CN ratio by utilizing the apparent increase in Kerr rotation angle when the reflectance of the recording medium is lowered by placing a dielectric film such as Sin or In between the magnetic thin film and the substrate. Proposed.

However, information is recorded and erased on magneto-optical recording media using semiconductor lasers, but when the disk rotational speed is increased to increase the information transfer speed, the laser irradiates a single point on the recording medium. As the beam irradiation time becomes shorter, the temperature of the recording medium of a semiconductor laser may not rise to the operating point for recording and erasing, that is, the Curie temperature.

An object of the present invention is to solve the above-mentioned problems and record data at high disk rotational speeds using a semiconductor laser without reducing the reproduction CN ratio, which has been improved by disposing a dielectric film between a magnetic thin film and a substrate. An object of the present invention is to provide a magneto-optical recording medium that allows recording and erasing on the medium.

[Failure to solve the problem]

In order to solve the above problems, the present invention provides a magneto-optical recording medium having a magnetic thin film having an axis of easy magnetization perpendicular to the substrate surface via a dielectric layer on a substrate. It is assumed that the film is an IN film.

[Effect]

By adding an appropriate amount of Sm to 81N, the regenerated CN ratio can be increased to 4.
! It is possible to secure more than MB and reduce the laser power required for recording and erasing the force signal.

〔Example〕

FIG. 1 is a sectional view showing the structure of a magneto-optical recording medium according to an embodiment of the present invention. That is, various dielectric layers 2 based on the present invention are laminated on a transparent substrate 1 made of glass, resin, etc., an amorphous magnetic thin film 3 of TbFe, TbFeCo, etc. is formed thereon, and a dielectric film made of a dielectric film is further formed. The protective layer 4 is laminated.

In the example described below, a 5.25-inch polycarbonate plate that has been sufficiently degassed is used as the substrate 1, and a Tb23F film formed by a sputtering method is used as the magnetic thin film 3.
Using es, CO8 or Tb24Fe7oCO6 film,
The protective layer 4 is made of the same material as the dielectric layer 2 using the same method.
A film was formed to a thickness of 100 nm.

Example]: This is an example in which AIN added with Sm is used as the dielectric layer 2. The formation of the dielectric layer 2 is, for example, 1 mmX] mmX
An AIN dielectric layer 2 containing 1.8 atomic % of Sm was formed by the RF magnetron sputter link method under the conditions of argon gas pressure of 0.6 Pa and sputtering power of 300 W using an IN sintered target embedded with Sm pieces with a size of 40 mm. After forming to a thickness of 9 Q nm, a TbFeCo alloy target was used without breaking the vacuum, and an argon gas pressure of 5
, QPa, and Tb24Fe by DC magnetron sputtering under the conditions of sputtering power of 300 W.
A 7oC06 thin film was laminated to a thickness of 70 nm as the magnetic thin film 3.

Furthermore, the same film as the dielectric layer 2 was formed thereon as a protective layer 4 to a thickness of 1100 nm by RF magnetron sputtering under the same conditions. Similarly, magneto-optical recording media having dielectric layers 2 with different Sm contents were produced by simply changing the Sm pieces embedded in the AIN sintered cuget. In a magneto-optical recording medium having a HIN dielectric layer containing 8 at% Sml, the optimum recording laser power P wOpt+ during signal recording, the erasing laser power Pa during signal erasing, and the CN ratio during signal reproduction were measured. However, both PWOpL+PR are 5. Qmlj, a sufficiently low value, and a reproduction CN ratio of 50 dB, which is much higher than the 45 dB required for digital recording. However, in the case of an AIN dielectric layer containing 9.5 at% of Sm, Pwapt is 5.0 ml, PC is 4,
Although it is not much different from OmW at 1.8 at%, the recycled CN
The ratio is 41 dB, which is less than 45 dB. In FIG. 2, the relationship between the Sm content and the regenerated CN ratio and Pwopt+PE is shown by lines 21 and 22.23, respectively. A] N dielectric layer 2
When the amount of Sm contained in Pw exceeds 0.3 at%. 1. .

When P begins to decrease and exceeds 7.5 at%, regenerated CN
The ratio deteriorates to 45 dB or less. In particular, when the Sm content is 1
．． In the range of 5 to 5.5 at%, the regenerated CN ratio is 49 to 5.
0dB, P, vo, t, P is 4.0 to 5. O
Almost uniform characteristics of mW can be achieved.

〔Effect of the invention〕

In a magneto-optical recording medium in which a perpendicularly magnetized film is a magnetic thin film,
Sm is added to the AIN film as a dielectric layer between the substrate and the magnetic thin film.
By containing 0.3 to 7.5 at.%, preferably 1.5 to 5.5 at.% of A recording medium was obtained, and recording and erasing by semiconductor laser irradiation became possible even when the disk rotation speed was increased.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional structural diagram of a magneto-optical recording medium according to an embodiment of the present invention, and FIG. 2 shows the content of Sm in the AIN film and the reproduction CN ratio.
FIG. 3 is a relationship diagram between optimum recording laser power and erasing laser power. 1 Substrate, 2 Dielectric layer, 3 Magnetic thin film, 4 (Heheda)
Yod "↓dOMd's cD dimension N '1" fN) Ball amount

Claims (1)

[Claims] 1) A magneto-optical device comprising a magnetic thin film having an axis of easy magnetization perpendicular to the substrate surface on a substrate via a dielectric layer, wherein the dielectric layer is an aluminum nitride film containing samarium. recoding media.